[SystemZ/ZOS] Implement setLastAccessAndModificationTime()

[Kai]

Summary

The function setLastAccessAndModificationTime() uses function futimens() or futimes() by default.
Both functions are not available in z/OS, therefore functionality is implemented using __fchattr() on z/OS.

[hubert.reinterpretcast]

llvm/lib/Support/Unix/Path.inc

801

Minor nit: As a function returning int (with 0 representing success), I would suggest using != 0 to check for the error condition.

[Kai]

Changed check for error condition according to review comment.

[abhina.sreeskantharajan]

LGTM!

llvm/lib/Support/Unix/Path.inc

#elif defined(HAVE_FUTIMES)
   Times[0] = sys::toTimeVal(
       std::chrono::time_point_cast<std::chrono::microseconds>(AccessTime));
   Times[1] =
       sys::toTimeVal(std::chrono::time_point_cast<std::chrono::microseconds>(
           ModificationTime));
   if (::futimes(FD, Times))
     return std::error_code(errno, std::generic_category());
   return std::error_code();
+#elif defined(__MVS__)
+  attrib_t Attr;
+  memset(&Attr, 0, sizeof(Attr));
+  Attr.att_atimechg = 1;
+  Attr.att_atime = sys::toTimeT(AccessTime);
+  Attr.att_mtimechg = 1;
+  Attr.att_mtime = sys::toTimeT(ModificationTime);
+  if (::__fchattr(FD, &Attr, sizeof(Attr)) != 0)
+    return std::error_code(errno, std::generic_category());
+  return std::error_code();
 #else
 #warning Missing futimes() and futimens()
   return make_error_code(errc::function_not_supported);
 #endif
 }
 
 std::error_code mapped_file_region::init(int FD, uint64_t Offset,
                                          mapmode Mode) {